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zhannawk [14.2K]
3 years ago
15

Which statement correctly describes an atom of the element helium? (9)

Chemistry
1 answer:
Luden [163]3 years ago
8 0

C. An atom of helium has its valence electrons in its first energy level, it wouldn't and can't satisfy the Octet rule as it only has 2 electrons, but with 2, it has a full shell, as the first energy level can hold only 2 electrons.

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If 2 CH3OH + 3 O2 -> 2CO2 + 4 H2O was carried out in the laboratory and 219 g of water was produced, what would the percent y
ANEK [815]

Answer:

Percent yield = 84.5 %

Explanation:

Given data:

Mass of methanol = 229 g

Actual yield of water = 219 g

Percent yield of water = ?

Solution:

Chemical equation:

2CH₃OH + 3O₂  →  2CO₂  + 4H₂O

Number of moles of methanol:

Number of moles = mass/ molar mass

Number of moles = 229 g/ 32 g/mol

Number of moles = 7.2 mol

Now we will compare the moles of water with methanol.

                        CH₃OH         :            H₂O

                            2               :               4

                           7.2             :           4/2×7.2 = 14.4 mol

Mass of water:

Mass = number of moles × molae mass

Mass = 14.4 mol × 18 g/mol

Mass = 259.2 g

Percent yield:

Percent yield = actual yield / theoretical yield × 100

Percent yield = 219 g / 259.2 g × 100

Percent yield = 84.5 %

7 0
2 years ago
Write the overall, balanced molecular equation and indicate which element is oxidized and which is reduced for the following rea
galina1969 [7]

Answer:

Cd(s) + AgNO₃(aq)  → Cd(NO₃)₂ (aq) + Ag(s)

Oxidized: Cd

Reduced: Ag

Explanation:

Cd(s) + AgNO₃(aq)  → Cd(NO₃)₂ (aq) + Ag(s)

Cd → Cd²⁺  +  2e⁻      Half reaction oxidation

1e⁻ + Ag⁺ → Ag           Half reaction reduction

Ag changed oxidation number from +1 to 0

Cd changed oxidation number from 0 to +2

Let's ballance the electrons

( Cd → Cd²⁺  +  2e⁻ ) .1

( 1e⁻ + Ag⁺ → Ag ) .2

Cd + 2e⁻ + 2Ag⁺  → 2Ag +  Cd²⁺  +  2e⁻

Finally the ballance equation is:

Cd(s) + 2AgNO₃(aq)  → Cd(NO₃)₂ (aq) + 2Ag(s)

4 0
3 years ago
Consider the following reaction: 2CH3OH ---> 2CH4+O2 delta H= +252.8kJ. Calculate the amount of heat transferred when 22.0g o
nydimaria [60]
To calculate the amount of heat transferred when an amount of reactant is decomposed, we must look at the balanced reaction and its corresponding heat of reaction. In this case, we can see that 252.8 kJ of heat is transferred per 2 moles of CH3OH used. When 22 g of CH3OH is used, 86.9 kJ is absorbed. 
4 0
2 years ago
Ethanol and water appear the saame to the naked eye at 25C. Which properties can help a chemist distinguish between? denisty, ma
Oxana [17]

Explanation:

As it is known that there are two types of properties. These are extensive and intensive.

Extensive properties : Properties that depend on the size or amount of system. For example, mass, volume etc.

Intensive properties : Properties that do not depend on the size or amount of system. For example, density, melting point, specific heat capacity etc.

On the basis of these properties water and ethanol are distinguished as follows.

  • Density of water is 997 kg/m^{3} whereas density of ethanol is 789 kg/m^{3}. Both these liquids can be separated by intensive properties.
  • Melting point of water is zero degree celsius whereas melting point of ethanol is -114.1 degree celsius.
  • Specific heat capacity of water is 4.184 J/g ^{o}C whereas specific heat capacity of ethanol is 2.46 J/g ^{o}C.
  • Mass of the given liquids cannot be differentiated because they will keep on changing depending on the quantity required. As mass is an extensive property, therefore, it is difficult to differentiate between the two liquids.

Thus, we can conclude that properties like density, melting point, specific heat capacity can help a chemist distinguish between ethanol and water.

7 0
3 years ago
One difference between mixtures and pure substances is that A) mixtures can be physically separated. B) mixtures are made of one
Alborosie
The answer your looking for is a)
 -please give me brainliest answer
5 0
3 years ago
Read 2 more answers
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